Phase 9: homebrew content + packs

- Homebrew entity (monster/spell/item/feat/condition) — Dexie v6, repo, hook,
  cascade-deleted with campaign
- Homebrew editor page: per-kind fields + description, create/edit/delete
- Compendium merges campaign homebrew of the matching kind (HB badge, generic
  HomebrewDetail) with the same cross-links (add monster->combat, spell/item->character)
- Content packs: export/import homebrew as JSON (validated, ids reassigned)
- System extensibility documented via the existing RulesSystem registry seam
- Fix: card editors (homebrew/npc/quest/note) debounce-save the FULL snapshot, not
  partial patches — editing two fields fast no longer drops an edit

New homebrew e2e + cascade test coverage.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/lib/db/db.ts

@@ -3,7 +3,7 @@ import type { Campaign } from '@/lib/schemas/campaign';
 import type { Character } from '@/lib/schemas/character';
 import type { Encounter } from '@/lib/schemas/encounter';
 import type { DiceRoll } from '@/lib/schemas/dice';
-import type { Note, Npc, Quest, Calendar, BattleMap } from '@/lib/schemas/world';
+import type { Note, Npc, Quest, Calendar, BattleMap, Homebrew } from '@/lib/schemas/world';
 import { characterDefaults } from '@/lib/schemas/character';
 
 /**
@@ -24,6 +24,7 @@ export class TtrpgDatabase extends Dexie {
   quests!: EntityTable<Quest, 'id'>;
   calendars!: EntityTable<Calendar, 'campaignId'>;
   maps!: EntityTable<BattleMap, 'id'>;
+  homebrew!: EntityTable<Homebrew, 'id'>;
 
   constructor() {
     super('ttrpg-manager');
@@ -66,6 +67,9 @@ export class TtrpgDatabase extends Dexie {
 
     // v5 — Phase 7 maps/VTT.
     this.version(5).stores({ maps: 'id, campaignId' });
+
+    // v6 — Phase 9 homebrew content.
+    this.version(6).stores({ homebrew: 'id, campaignId, [campaignId+kind]' });
   }
 }